Polyamide substrates, such as nylon carpeting, upholstery fabric and the like, are subject to staining by a variety of agents, e.g., foods and beverages. An especially troublesome staining agent is FD&C Red Dye No. 40, commonly found in soft drink preparations. Different types of treatments have been proposed to deal with staining problems. One approach is to apply a highly fluorinated polymer to the substrate. Another is to use a composition containing a sulfonated phenol-formaldehyde condensation product.
For example, Liss and Beck, in U.S. Pat. Application Ser. No. 124,866, filed Nov. 23, 1987, disclose stain-resistant synthetic polyamide textile substrates having modified sulfonated phenolformaldehyde polymeric condensation products. However, sulfonated phenol-formaldehyde condenation products are themselves subject to discoloration; commonly they turn yellow. Yellowing problems are described by W. H. Hemmpel in a Mar. 19, 1982 article in America's Textiles, entitled Reversible Yellowinq Not Finisher's Fault. Hemmpel attributes yellowing to exposure of a phenol-based finish to nitrogen oxides and/or ultraviolet radiation. Critchley et al., Heat Resistant Polymers; Technoloqically Useful Materials, Plenum Press, N.Y. 1983, state that the thermo-oxidative stability of phenol-formaldehyde condensation products can be improved by etherifying or esterifying the phenolic hydroxyl groups.
To deal with the yellowing problem, Marshall, in U.S. Pat. No. 4,833,009 removes color-formers by dissolving the condensation product in aqueous base, acidifying the solution to form a slurry, heating the slurry so as to cause phase separation, recovering water-insoluble material and dissolving the water-insoluble material in aqueous base. On the other hand, Liss and Beck, in their aforesaid application, remove color-formers by acylating or etherifying some of the phenolic hydroxyls of the condensation product, and in a preferred embodiment, dissolving the modified condensation product in a hydroxy-containing solvent, such as ethylene glycol, prior to its being applied to the textile substrate.
Allen et al., in U.S. Pat. No. 3,835,071, disclose rug shampoo compositions which upon drying leave very brittle, non-tacky residues which are easily removed when dry. The compositions comprise water-soluble metal, ammonium or amine salt of a styrene-maleic anhydride copolymer, or its half ester, and a detergent. Water-soluble metal salts of Group II and the alkali metals (particularly magnesium and sodium) are preferred and ammonium salts are most peeferred by Allen et al.